Lubricating composition



2,703,786 LUBRICATING CGMPOSITION David W. Young, Roselle, and Delmar L. Cottle, Highland'lark, N. 5., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application June 19, 195i, erial No. 232,450

h Claims. (Cl. 252-2.7)

This invention relates to lubricating oil compositions. Particularlythe invention relates to lubricating oil compositions having desirable lubricating properties under conditions conducive to oxidation and sludge formation. More particularly the invention relates to a new and improved lubricating oil composition containing combined therein a metal derivative of a phenol sulfide, a small amount of a higher alcohol, and an N-acyl p-amino phe- 1101.

It has previously been found that the N-acyl p-amiuo phenols of a certain range of acyl group chain length are outstanding oxidation inhibitors for many types of organic materials. Their use as oxidation inhibitors for solid hydrocarbon materials such as waxes, synthetic rubbers and the like, is set out in copending application Serial No. 185,326, now Patent No. 2,654,722. it has also been found that certain of these N-acyl p-amino phenols have outstanding utility as anti-oxidants for lubricating grease compositions which is set out in detail in copending application Serial No. 186,318, now abandoned.

The desirable oxidation resistance, non-staining characteristics of these N-acyl p-amino phenols have been unavailable for utilization in lubricating oil compositions heretofore however, because of the insolubility of such acyl amino phenols in mineral lubricating oils. In some oxidizable organic materials, notably synthetic rubbers, such as butyl, Vistanex, and G. R. 8., the oxidation resisting effect of these N-acyl p-amino phenols is obtained when the phenol exists in the form of a minute particulate dispersion throughout the material; complete solution of the phenol not being necessary. In a lubricating oil'composition, however, the anti-oxidant must exist in solution for its oxidation resisting effect to be realized.

It has now been found, and forms the object of this invention, that mineral oil solutions of these desirable N-acyl p-amino phenols, may be prepared by the use of small amounts of a combination of a metal derivative of a phenol sulfide, and a higher alcohol, that the combination acts as a solubilizing agent for the phenol as well as imparting other desirable properties to the mineral oil composition, set out below.

Briefly stated the invention comprises a mineral lubricating oil containing combined therein:

(1) An oil soluble metal derivative of a phenol sulfide, (2) A higher alcohol, and (3) An N-acyl p-amino phenol.

The mineral oils operable as the base for these new and improved lubricating compositions include any of the lubricating oils obtained from petroleum crudes, whether naphthenic or parafiinic in nature. The oils operable may have been extracted from their crude bases by any of the means known to the art and purified or refined by'any number of refining techniques. The viscosity ranges of the oils used will be dictated only by the lubricating application itself, any of the viscosities within the range of from to 500 S. U. Set 210? F., the range generally defining a lubricating oil, being acceptable. It is preferred to form the improved lubricating compositions of this invention from a naphthenic crude distillate having a viscosity within the range of from 30 to 500 S. U. S. at 210 F.

The first additive constituent of the improved mineral lubricating oil compositions of this invention is a metal derivative of an alkyl phenol sulfide. These compounds include metal salts having the general empirical formula:

M{ [-OAr (R) 128:0}n wherein M is a metal selected from the group of sodium, potassium, magnesium, calcium, barium, aluminum, tin, zinc, cadmium, cobalt, and nickel; n is the valence of the metal; x is one or more; R represents one or more alkyl groups having enough carbon atoms, preferably a I mates Paten ed Map ,8. 1955 total of at least 10 in the molecule, Lto insure solubility of the compound in mineral oil. r 1 5 I Y The compounds included within the general formula above that are preferred in-this invention are the metal salts of the alkyl phenol sulfides represented by thefollowing formula:

wherein M represents a metal as above (in the case ofpolyvalent metals, other valences than that connected to the oxygen in this formula may be joined to other inorganic or OIgQIllC groups such as halogen, sulfur, oxygen, alkyl and aryl groups, residues of alcohols, phenolic compounds, mercaptans, organic and inorganic acids, such as )R and SR in which R" represents an organic or inorganic group or radical).

R represents an orgariic group .which maybe either aryl, alkyl, aralkyl or alkyl-aryl and'vvhich may contain substltuent groups, such as. halogen, particularly chlorine, also nitro, mtroso, amino, hydroxy, -c'arboxy, .alkoxy, aroxy, mercapto groups and the like, and R represents an organic group of the same' class as R, preferably an alkyl group of from 5 to 20.carbon atoms.

The hexagon in the formula above represents an aromatic nucleus containing one or more benzene rings; or a condensed ring system such asnaphthalene or-the' like: The position of the various groups attached to the hexagon are not lun ted to those shownabove, but may also be in any position ortho, meta, or para to-each other.

The sulfur atom represented by,S.;in the above formula may be substituted by selenium or-tellu-rium. The. subscript x may be, any integer froml to:,5, and is preferably 1 to 2.

Metal salts of the" following classes of alkyl phenol sulfides are particularly desirablezas'the'first additive corn ponent of the improved mineral lubricating-oil compositions of this'invention: g f

l. Alkyl phenol thio others v III. Polymers of alkyl phenol sulfides 0H on I In all the Formulae I-IV, R represents an alkyl group containing from 3 to 20 carbon atoms, preferably 4-8 carbon atoms.

The metal salts of the above classes of compounds are formed by replacing the hydrogen atom of the hydroxyl group by a suitable metal such as those described above. In the case of polyvalent metals the metal may be connected -to two hydroxyl groups of the same molecule or it may join two different molecules. Illustrative salts are represented by the following formulae:

(R, R, and S: are as described above.)

If desired any of the above described metal derivatives of alkyl phenol sulfides may be subsequently treated with compounds of the type of Pxsy to impart additional desirable characteristics. Phosphorus pentasulfide treat ment of the barium salt of tertiary octyl phenol sulfide, for example, adds desirable extreme pressure resistant characteristics to the phenol sulfide.

The compounds described above are or outstand ng utility for use in mineral lubricating oils tor improving the pour and cloud points, for flushing compositions, when combined with low viscosity oils, and have a sludgedispersing or detergent action which substantially mproves general engine cleanliness under severe operating conditions. Their preparation is specifically set out in United States Patent No. 2,362,289, issued to Louis A. Mikeska November 7, 1944, and United States Patent No. 2,346,808, issued to Carl Winning and John G. McNab on April 18, 1944.

The second of the three additive constituents of the improved mineral oil compositions of this invention is broadly described as a higher alcohol.

The higher alcohols to be used in coinunction with the metal compounds are preferably those having 8 carbon atoms or more, though in general alcohols falling in the C12 to C20 range are preferred. The alcohols may be saturated straight and branched chain aliphatic alcohols such as octyl alcohol, CBIIHOH, lauryl alcohol, CizHzsOH, cetyl alcohol, CisHssOH, stearyl alcohol, sometimes referred toas octadecyl alcohol, C18H3IOH, and the like; the corresponding olefinic alcohols such as oleyl alcohol; cyclic alcohols, such as naphthenic alco F hols; and aryl substituted alkyl alcohols, for instance, phenyl octyl alcohol or octadecyl benzyl alcohol or mixtures of these various alcohols, which may be pure or substantially pure synthetic alcohols. One may also use mixed naturally occurring alcohols such as those found in wool fat (which is known to contain a substantial percentage of alcohols having about 16 to 18 carbon atoms) and in sperm oil (which contains a high percentage of cetyl alcohol); and although it is preferable to isolate the alcohols from those materials, for some purposes, the

wool fat, sperm oil or other natural products rich in alcohols may .be used per se. Products prepared synthetically by chemical processes may also be used such as alcohols prepared by the oxidation of petroleum hydrocarbons, e. g. paratfin wax, petrolatum, etc., or those alcohols prepared by the Oxoj process. One particularly outstanding alcohol for this use is the commercial mixture of alcohols obtained on the hydrogenation of coconut oil. The mixture having an average chain length of 13.5, known commercially as Lorol B; is es pecially useful.

The third additive constituent of the composit1ons of invention is generally described as N-acyl p-ainino phenols. These compounds are represented by the gem eral formula: R

. H o no rI-b-Jt 4 where R is an alkyl group containing from 3 to 24 carbon atoms, preferably non-benzenoid in nature, and R and R" are alkyl groups containing from 1 to 20 carbon atoms, or hydrogen atoms.

The preferred embodiment of the invention contemplates the use of compounds according to the formula above where R is an alkyl group containing from 3 to 18 carbon atoms and R and R are hydrogen, i. e., the N- acyl p-amino phenols. However, the alkylated acyl pamino phenols, exemplified by the formula above, R and R" being alkyl groups containing from 1 to 20, preferably 4 to 15 carbon atoms, are also very satisfactory as oxidation inhibitors. Compounds such as N-n-valeryl- 4-amino-3-pentadecyl phenol, (N-n-pentanoyl-4-amino- 3 pentadecyl phenol), N-n-propanoyl 4 amino-3 pentadecyl phenol, N-n-pentanoyl 4 amino 2,6,di-tertiary butyl phenol, N-n-hexoyl-4-arnino-2-hexyl phenol are examples of the alkylated acyl-p-arnino phenols operable.

The preparation of these acyl p-arnino phenols is achieved by admixing the desired acid or acid chloride with p-amino phenol and heating the mixture under proper conditions. The reaction progresses smoothly, splitting oif water (or hydrogen chloride) and giving the desired acylated amino phenols which may be purified by any of the various methods known to the art such as distillation, crystallization, extraction, etc.

As the acidic constituent of the reaction mixture, any organic acid containing from 3 to 24 carbon atoms may be combined with the p-amino phenol. The compounds especially preferred as oxidation inhibitors, however, are those long chain fatty acids or fatty acid chlorides containing from 4 to 19 carbon atoms per molecule.

It may be found convenient in some instances to prepare the compositions of invention in such manner that the desired acyl p-amino phenol is formed in situ. This preparation may be accomplished in the following manner.

To a heated oil solution there may be added the calculated amount of a p-amino phenol. The desired acid or acid chloride may then be added, the formation of the acyl p-ainino phenol taking place upon the addition of the acidic constituent.

After the reaction is completed the mixture is stripped with heat, and Water is removed.

The three constituents described above are blended with the selected mineral oil in the following proportions:

(a) From 0.2% to 10%, preferably 0.4% to 5.0% of the metal derivative of the alkyl phenol sulfide,

(11) From 0.1% to 5.0%, preferably 0.1% to 3.0%, of

the higher alcohol, and

(c) From 0.1% to 5.0%, preferably 0.1% to 3.0%, of

the N-acyl p-amino phenol percentages being by weight, based on the weight of the total composition.

The compositions are prepared quite easily, it being necessary to merely mix the desired amounts of the additive materials with the mineral lubricating oil chosen, heat to within 220-300" F., and allow to cool.

To illustrate more completely the concept of this invention the following experimental data is presented. It is to be understood that this data serves as illustration only and is not to be considered as limiting operability in any manner.

EXAMPLE I To illustrate the solvating effect of the materials described above on the N-acyl p-amino phenols the follow ing procedure was carried out.

To a highly refined mineral oil distillate from :1 mph thenic crude having a viscosity at 210 F. of about S. U. S., hereinafter referred to as Oil A, 0.1% by weight of N-palrnitoyl p-amino phenol was added. The mixture was heated to about 240 F. and then cooled. A cloudy solution indicated that the phenol was not soluble in the mineral oil. To a second sample of Oil A there was added 0.1% by weight of the same phenol. and 2.5 weight percent of a composition having the following formula:

40.0% of a highly refined parafiinic distillate having a viscosity at 210 F. of about 55 S. U. S.

. The active ingredient present in the blend therefore was'1.25 weight percent of the metal derivative of the phenol sulfide and .02% of the alcohol. This composition will be referred to hereinafter as Detergent Inhibitor A. Its preparation is described in detail in United States Patent No. 2,294,145.

The mixture was heated to about 240 F. and then cooled to room temperature. A brilliant solution re sulted indicating that the Detergent Inhibitor A acted as a solvating agent for the phenol. To show that a composition according to the concept of this invention is necessary to solubilize the phenols, the following experiments were run.

100 ml. of an 'oil of viscosity index of 55 was treated with 0.25% N-palmitoyl-p-amino phenol. The solution was heated for 4 hours at 230 F. with good agitation, and then cooled to 30 C. Some cloud developed in the oil in about two minutes time. Tests indicated the cloud material was N-palmitoyl-p-amino phenol.

The solution was then treated with 1.25% by weight of the barium salt of diis'obutyl phenol sulfide and then heated to 230 F. for 4 hours. Upon cooling the cloud once again developed in the oil at 25 C. to 30 C. Tests indicated that the cloud was formed by insoluble N-palmitoyl-p-amino phenol.

In another experiment it was found that 0.25% of N'palmitoyl-p-amino phenol was not soluble at 25 C. in a blend of 97% of the oil used above and 3% mixed alcohols obtained from hydrogenated coconut oil.

EXAMPLE 11 To show the enhanced corrosion resistance of the materials of invention several compositions were submitted to the Standard Oil Development copper-lead alloy automotive bearing corrosion test. This test, which serves as a measure of the bearing corrosion properties of a lubricant, is conducted as follows:

500 cc. of the oil to be tested is placed in a glass oxidation tube (13" long and 2% in diameter) fitted at the bottom with a A bore air inlet tube perforated to facilitate air distribution. The oxidation tube is then immersed in a heated bath so that the oil tested is maintained at 325 F. during the test. Two quarter sections of automotive bearings of copper-lead alloy of known weight having a total area of 25 square centimeters are attached to opposite sides of a'stainless steel rod which is then immersed in the test oil and rotated at 600 R. P. M., thus providing sufficient agitation'of the sample during the test. Air is then blown through the oil at the rate of 2 cu. ft. per hour. bearings are washed and'weighed at the end of each four hour period and then polished and reweighed before continuing for another period.

The results of'this testing procedure on several blends in accordance with the concept of this invention are set out in detail below. Since the bearing weight loss varies inversely'with the oxidation resisting or corrosion resistance of the oil blend, higher losses indicate a less desirable blend.

Table I s. 0. D. GORROSIONTEST RESULTS 1 Oil A-A highly refined naphthenie distillate having a viscosity at 210 F. of about 65 S. U. S.

It will be noted from the data of Table I above that the blends containing the N-acyl p-arnino phenol solvated by the metal salt of the alkyl phenol sulfide gave excellent results in the S. O. D. corrosion test. The weight loss in milligrams was reduced from 62.8 in the case of the uninhibited oil and from 28 in the case of the inhibited oil to To increase the severity of the/test the 21, 15.9, and 9.0 mg. weight loss in the case respectively of the C 2 and the C4 acyl derivatives of the phenol.

EXAMPLE III In a second series of O. D. Bearing Corrosion Tests a detergent inhibitor having the following composition was employed:

63.5 of high barium content diisobutyl phenol sulfide 37.5% of high alkalinity calcium sulfonate This composition which is useful as a detergent inhibltor and general engine cleanliness agent will be hereinafter referred to as Detergent Inhibitor B. Details of the preparation of the calcium sulfonate are set out in United States Patent No. 2,467,176.

Into a sample of the highly refined naphthenic distillate referred to above (Oil A) there was added 0.25% by weight of N-palmitoyl p-amino phenol. The mixture was heated to about 240 F. and allowedto cool to room temperature. There resulted a cloudy emulsion indicatmg that the phenol was insoluble in the oil. To the mixture was then added 2.5% of the detergent inhibitor described above, Detergent Inhibitor B and the total mixture heated to about 240 F. On subsequent cooling a brilliant solution was obtained at temperatures as low as 20 F., indicating that the Detergent Inhibitor B was an excellent solvating or solubilizer for the N-acyl p-amin'o phenol.

In an experiment it was found that 2.0% high alkalinity calcium sulfonate would not solvate 0.25 N-palrnitoyl p-ammo phenol in an oil having a viscosity index of 55. A precipitate formed when the solution cooled to 30 C.- showmg that the calcium sulfonate alone is not the active ingredient.

The S. O. D. Corrosion Test described above was run on these oil blends as follows:

I Table II s. 0.1). CORROSION 'rns'rs The results indicate that the oil blend containing the N-acyl p-arnino phenol is outstanding in its corrosion resisting effect and that the solvated acyl amino phenol is a very effective oxidation inhibitor.

EXAMPLE IV In a second form of oxidation test, that is, a procedure designed to test the oxidation inhibiting efiect of the additive materials, ml. of a highly refined parafiinic distillate having a viscosity at 210 F. of 52 S. U. 8., hereinafter referred to as Oil B, was the base oil used. The base oil alone and samples containing the additives as described above were held for 128 hours at a temperature of 250 to 260 F. in a Freas oven. A standard copper lead bearing was placed in each of the samplesand the bearing weight loss calculated at the termination of the test. Test results are given in Table III below.

Table III OXIDATION TEST RESULTS Bcarln No. Base Oil Additive wt. 1.055

None; 13 2.5% Detergent Inhibitor B 8 2.5% Detergent Inhibitor B 25% N-lnuryl p-amino phenol. 3

It will be notedthat the oil composition of this inventron, that is, Experiment No. 3, reduced the bearing weight loss from 13 to 3 mg. This is an example of the excellent ox dation resistance characteristics of the compositions of this invention.

EXAMPLE y In another type of oxidation test a silver hearing was immersed in 150 ml. of the oil to be tested. The oil was held for 128 hours at the temperature of 250 to 260 F. in a Freas air oven. The loss in weight of the silver bearing was calculated at the termination of the test. Results are set out in Table IV below.

Table IV OXIDATION TEST RESULTS It will be seen that whereas the base oil alone lost a total of 112 mg. in weight under the test conditions, the blend containing 8% of the detergent inhibitor actually caused a 10 mg. gain in weight, the composition of the invention causing a 4 mg. gain in weight.

It has also been found that the combination of the metal derivative of the alkyl metal sulfides and the higher alcohols described above also exert a solvating eifect on other types of anti-oxidants. For example, the 6-ethoxy 2,2,4-trimethyl-L2 dihydroquinoline compounds which has excellent anti-oxidation effect when blended with mineral lubricating oils is found to be insoluble in concentrations in the neighborhood of from 0.05 to 2.0 weight percent. In one experiment 0.1% of this compound was added to a highly refined paraffinic distillate having a viscosity at 210 F. of 43 S. U. S. and the viscosity index of 112. The blend was heated to 240 F. and upon cooling the anti-oxidant precipitated from the oil.

In a second experiment 2.5% of the Detergent Inhibitor B, as described above, was added to the blend of 0.1% of the dihydroquinoline and mineral oil. In this instance the blend, after being heated to 240 F., was in the form of a brilliant solution, the anti-oxidant remaining in perfect solution even upon cooling to low temperatures.

Other anti-oxidants of this nature, for example the Diphenylol propane HaCCGHr.

Diphenylol methane may be solvated by the detergent inhibitors as described above.

The lubricants from which'these improved compositions are prepared may also contain dyes, metalhc or other soaps, pour inhibitors, sludge dispersers, oxidation nhibitors, thickeners, viscosity index improvers such .as soluble linear polymers, oiliness agents, .resins, rubber, fatty oils, heat thickened fatty oils, sulfurized fatty oils, extreme pressure lubricating agents, organo-metallic compounds, bright stocks (such as refined petroleum lubrieating 011 residues), voltolized fats, mineral oils and/or waxes, colloidal solids such as graphite, zinc oxide, etc., and the like. 1 To summarize briefly this invention relates to new and mproved lubricating oil compositions having outstandmg desirable anti-oxidation characteristics which consist essentially of a mineral lubricating oil which contains a mmor amount of a metal derivative of an alkyl phenol sulfide, a mmor amount of a higher alcohol, and a minor amount of an N-acyl p-amino phenol.

What is claimed is:

1. An improved lubricating oil composition having outstanding resistance to oxidation which comprises a mineral lubricating oil containing combined therein from 0.2% to 10.0% by weight of an oil soluble metal derivative1 of an alkyl phenol sulfidehaving the general-for mu a weight of an N-acyl p-amino phenol having the followmg formula:

wherein R1 is an alkyl group containing from 4 to 19 carbon atoms and wherein R2 and R3 are selected from the group consisting of hydrogen and alkyl groups containing from 1 to 20 carbon atoms.

2. A lubricating oil composition according to claim 1 wherein M represents barium and wherein R represents an alkyl group containing 8 carbon atoms.

3. A lubricating oil composition according to claim 1 wherein said higher alcohol has an average number of carbon atoms of 13.5 and is derived from coconut oil.

4. A lubricating composition according to claim 1 wherein R2 and R3 are hydrogen.

5. A lubricating oil composition according to claim 1 wherein said N-acyl p-amino phenol is N-lauroyl pamino phenol.

6. A lubricating oil composition according to claim 1 wherein said N-acyl p-amino phenol is N-palmitoyl pamino phenol.

7. A lubricating oil composition according to claim 1 wherein said N-acyl p-amino phenol is N-stearoyl 3- pentadecyl p-amino phenol.

8. A lubricating oil composition which comprises a mineral lubricating oil containing combined therein from 0.5 to 5.0 weight percent of the barium salt of di-isobutyl phenol sulfide, from 0.1 to 3.0 weight percent of a mixture of alcohols obtained on hydrogenation of coconut oil and having an average number of carbon atoms of 13.5 and from 0.1 to 3.0% by weight of N-lauroyl p-amino phenol.

9. A lubricating oil composition which comprises a mineral lubricating oil containing combined therein from 0.5 .to 5 .0 weight percent of the barium salt of di-isobutyl phenol sulfide, from 0.1 to 3.0 weight percent of a mixture of alcohols obtained on hydrogenation of coconut oil and having an average number of carbon atoms of 13.5 and from 0.1 to 3.0% by weight of N-palmitoyl p-amino phenol.

Winninget al. A Aug. 25, 1942 Morway et a1 July 22, 1952 

1. AN IMPROVED LUBRICATING OIL COMPOSITION HAVING OUTSTANDING RESISTANCE TO OXIDATION WHICH COMPRISES A MINERAL LUBRICATING OIL CONTAINING COMBINED THEREIN FROM 0.2% TO 10.0% BY WEIGHT OF AN OIL SOLUBLE METAL DERIVATIVE OF AN ALKYL PHENOL SULFIDE HAVING THE GENERAL FORMULE 